yeah, there is alot of stress going through the gearbox cases… I am not an engineer, but having built gyrocopters, I sort of know how metal and fatigue can slowly work at things and cause cracks from any weak spot… like holes, rough edges and welding.
From what I have read and researched, I am thinking that probably a good nylon case set is the most likely to survive the rigors, yes, they may eventually crack or break… but they only cost $10 bux from China to replace. Maybe weak spots can be strengthened by arolditing some fiberglass cloth over certain areas… smoothing rough edges… smoothing holes before using.
For me, I would rather not spend up to $200 on metal gearbox cases… which unless they are made of single crystal titanium, may also crack, cast alloy, and that cast ‘muck metal’ like the dinky toys… all have large porous grains in them when looked at under a magnifying system, so prone to cracking… CnC.d from a billet would obviously be best… but the cost?
I think I will just buy a bunch of nylon cases and replace them as needed… hopefully, from this thread, I may be able to reinforce notoriously weak spots… and look for the main causes of the cracks beginning.
One thing I think may be one cause of cracking, is the final gear that runs the ladder retracting the plunger… in nylon (or plastic) the gear is a little out of balance and carries little mass to cause harmful vibration… but when a metal gear is used, the out of balance is probably quite large… causing large forces in the box… forces the cases have to deal with…
I am thinking that balancing this gear may give the cases an easier time? My metal gear sets are due any time, I will be checking this gear for balance and maybe trying to balance it, to try and get nylon cases to last longer.
Has anyone tried balancing any of the metal gears?